Temperature sensitive valves mounted in a cylinder block of an internal combustion engine for releasing a lubricating oil to the outside of an oil passage in response to a temperature of the lubricating oil flowing in the oil passage are known as disclosed, for example, in Japanese Patent Application Laid-open Publication (JP-A) No. H08-93430.
As shown in FIG. 7 of JP H08-93430A, a cylinder block includes a lubrication oil supply passage, a bypass hole, a through-hole, and a temperature sensitive valve.
The bypass hole is closed by a top surface of the temperature sensitive valve. As the temperature of a lubricating oil goes down, the temperature sensitive valve contracts, causing the top surface of the temperature sensitive valve to separate from the bypass hole. Thus, the lubricating oil in the supply passage is allowed to bypass the temperature sensitive valve and discharged from the through-hole. By thus releasing the lubricating oil at a low temperature, it is possible to lower the engine loads to thereby reduce fuel consumption of the internal combustion engine.
In general, a valve mechanism is constituted by a valve and a valve casing in which the valve is housed. In case of JP H08-93430A, the cylinder block corresponds to the valve casing, and the temperature sensitive valve corresponds to the valve. A distance between the bypass hole and the temperature sensitive valve provides a valve opening. Thermal performance of the valve mechanism can be determined by a correlation between the lubricating oil temperature and the valve opening.
In the structure shown in JP H08-93430A, the temperature sensitive valve and the cylinder block are immersed in a liquid tank or placed in a thermostatic tank when determining thermal performance of the valve mechanism. The temperature sensitive valve is a small-sized component, however, the cylinder block is a medium-sized or large-sized component, so that performance determination of the valve mechanism necessarily involves high cost.
A demand for a reduction in cost of the cylinder block or the like structural member also causes a need for a technique which is capable of reducing cost for performance determination of the temperature sensitive valve.